RFR: 8257146: C2: extend the scope of StressGCM

Thu Nov 26 21:43:00 UTC 2020

On Thu, 26 Nov 2020 20:36:53 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

> Extend the scope of StressGCM by allowing it to move instructions into basic blocks with worse frequency. This should improve StressGCM's ability to expose bugs where C2 relies on GCM heuristics for correctness.
> 
> Tested with StressGCM enabled on `hs-tier1-3` and a single repetition, the following test cases fail on `linux-aarch64-debug` and require further investigation:
> - `serviceability/sa/ClhsdbJstackXcompStress.java`
> - `compiler/c2/cr6663848/Tester.java`
> 
> Also tested with StressGCM disabled (default)  on `hs-tier1-3`, all tests pass.

Extend the scope of StressGCM by allowing it to move instructions into basic
blocks with worse frequency.

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PR: https://git.openjdk.java.net/jdk/pull/1469